1. Field of the Invention
The present invention relates to a module including a substrate on which an IC is mounted, the IC including a modulation circuit unit configured to modulate a baseband signal into an RF signal and a demodulation circuit unit configured to demodulate an RF signal into a baseband signal.
2. Description of the Related Art
Previously, a known module in which an IC is mounted on the surface of a substrate, such as a low temperature co-fired ceramic (LTCC), a multilayer resin substrate, or other suitable substrate and an electrical circuit, such as a balun, a filter, or other suitable electrical circuit connected to the IC has been provided. An example of such a module is disclosed in Japanese Unexamined Patent Application Publication No. 2007-243559 (see, for example, paragraphs [0025] to [0027] and FIGS. 1, 7, and 8). In a module 500 illustrated in FIG. 4A of this application, an IC 502 and various types of surface-mount devices 503 are mounted on the principal surface of a multilayer substrate 501, and electrical circuits, such as a coil 504, a capacitor 505, a balun 506, a filter 507 are provided in a predetermined region inside of the multilayer substrate 501.
As illustrated in FIG. 4B, the balun 506 is provided in a layer L0 to a layer L12 of the multilayer substrate 501, and the main portion thereof is provided in the layer L6 to the layer L12. More specifically, in the layer L10 and the layer L11, an unbalanced-side wiring pattern 508 is provided, into which an RF signal in an unbalanced state is input, the RF signal being input from an antenna terminal (not shown) and being subjected to a predetermined filtering process, and in the layer L9, a balanced-side wiring pattern 509 is provided that is electromagnetically coupled to the unbalanced-side wiring pattern 508 and outputs to the IC 502 the RF signal converted into a balanced state, thereby defining the balun 506.
Using a wiring pattern provided in the layer L11, a coil pattern 508a and a coil pattern 508b provided in the layer L10 are connected to each other through interlayer connection conductors (via conductors), the insides of via holes of which are filled with conductive paste, thereby providing the unbalanced-side wiring pattern 508. In addition, the coil pattern 508a is connected to an input terminal 510 through an interlayer connection conductor 510a provided in the layer L0 to the layer L9.
The balanced-side wiring pattern 509 includes a coil pattern 509a and a coil pattern 509b formed in the layer L9. In addition, the coil pattern 509a is connected to an output terminal 511 through an interlayer connection conductor 511a formed in the layer L0 to the layer L8, and the coil pattern 509b is connected to an output terminal 512 through an interlayer connection conductor 512a formed in the layer L0 to the layer L8, thereby forming the balun 506 indicated by an equivalent circuit in FIG. 4C.
In addition, as illustrated in FIG. 4A, the filter 507 is provided adjacent to the balun 506, in the layer L0 to the layer L6 of the multilayer substrate 501, and the filter 507 subjects the RF signal input from the antenna terminal to predetermined signal processing. In addition, FIGS. 4A to 4C are diagrams illustrating an example of the module 500 of the related art, and FIG. 4A is a cross-sectional view, FIG. 4B is a diagram for explaining a wiring pattern forming the balun 506, and FIG. 4C is a diagram illustrating the equivalent circuit of the balun 506.
Incidentally, while the RF signal in a balance state, output from the balanced-side wiring pattern 509 of the balun 506, is input to the IC 502 through the output terminals 511 and 512, the filter 507 and the various types of electrical circuits 504 and 505 are provided adjacent to the interlayer connection conductors 511a and 512a, in the layer L0 to the layer L8 in which the interlayer connection conductors 511a and 512a (connecting wirings) electrically connecting the balanced-side wiring pattern 509 to the output terminals 511 and 512 are provided. Accordingly, due to electromagnetic coupling between the wiring pattern, which forms the filter 507 and the various types of electrical circuits, such as the coil 504 and the capacitor 505, and the interlayer connection conductors 511a and 512a, a noise signal flowing from the antenna terminal into the filter 507 or into the various types of electrical circuits 504 and 505 may propagate to the interlayer connection conductors 511a and 512a and flow into the IC 502. Therefore, the IC 502 may malfunction as a result of the noise signal flowing to the IC 502.